What would be a good 12v dc circ pump for overheat zone?

[dogwood]

I am going to install a 12v circ pump on my Solo Innova's overheat zone. The zone consists of about 35 feet of Slantfin baseboard hung on a wall behind the boiler. It will be powered by a deep cycle marine battery or two kept energized by a trickle charger. I could use some recommendations on what would be a good 12v pump for this application. The ones I've seen so far online suitable for a hydronics application have been pricey (several hundreds). The pump will only see occasional use so I was hoping not to pay a fortune for one, but will if necessary to have a reliable overheat zone. The electricity here goes out with some frequency. Any suggestions. would be appreciated. Thanks.

Mike

 

[peakbagger]

DC pumps used for solar hot water would work well but they aren't cheap

http://www.thesolar.biz/dc_hot_water_circulating_pumps.htm

I have an 12 year old March pump on my SHW system, I have spare sitting in a box but the March just keeps on running. Lower budge would be pumps used on sailboats but check the temp ratings. Hamiton Marine has quite few brands and models

 

[dogwood]

Thanks Peakbagger. The exact site your link goes to was the one that surprised me with the cost of dc circs for higher temp hydronics applications. I'll check out the Hamilton Marine site too.

Mike

 

[arngnick]

Kind of goes without saying but make sure your overheat loop is setup to take advantage of thermosiphon effect. I believe this will go a long way. On my boiler I am going to rely only on thermosiphon. 1. in the overheat loop and 2. My storage is also setup so it can take heat by thermosiphon. Rarely lose power so not to much work for me.

 

[dogwood]

Arngnick, thermosiphon is what I originally plumbed my overheat zone to work on, but I think I screwed up the configuration of the zone and don't trust it to work. https://www.hearth.com/talk/threads/another-dump-zone-design.101636/. I have seven five foot sections of baseboard, one over the next, mounted on a wall directly behind the boiler. Picture a ladder. The seven five foot sections of baseboard would be the rungs, the one inch supply and return pipes the side rails. Its a little like Jebatty's overheat zone. https://www.hearth.com/talk/threads/the-tarm-has-landed-again-the-move-into-the-new-shop.51267/, except not so high up and with shorter horizontal sections.

I was thinking instead of teeing off the horizontal sections of baseboard from the vertical supply and return pipes, I could replace the tees with elbows to make the sections of baseboard one continuous run. Then use a battery powered pump to push the water through in the event of a power failure. However, I wasn't expecting the 12v circ pumps to be a pricey as they are relative to TACO or Grundfoss 120v circs.

The other alternative would be to move the overheat zone, as is, to the ceiling like Kopeck has his overheat loop https://www.hearth.com/talk/threads/a-few-pictures-of-our-boiler-systems.75006/page-5 and leave it as thermosiphon only. Maple suggested doing that in my above linked thread . A lot less expensive that way, but the more I think about it now the more that that seems a good way to go.

Lots of work, or lots of money. Seems like that's always the way. Thanks for your input Arngnick.

Mike

 

[arngnick]

How about getting a DC to AC power inverter to run a cheap 120v circ? The circulators ussually only pull between .5 to 1 amps. So you would need a 1000W inverter at most.

 

[dogwood]

Good idea arngnick. I'll cost it out.

Mike

 

[mustash29]

A 1000 W inverter sounds like overkill just to run a circ pump. I think I would try something around 200 - 400 watt instead. A 120 VAC circ @ 1 amp is going to draw 120 watts, and pull 10 amps from the battery @ 12 VDC. I can's see a small circ (like a Taco) having anything significant for starting current surge.